Stabilized phenyl-hydrazine



2,701,815 Patented Feb. 8, 1955 STABILIZED PHENYL-HYDRAZINE Reinhard Biiker and Hans Georg Fuchs, Frankfurt am Main, Germany, assignors to Farbwerke Hoechst Aktiengesellschaft vormals Meister Lucius & Bruning, Frankfurt am Main Hochst, Germany No Drawing. Application October 27, 1953, Serial No. 388,656

Claims priority, application Germany October 29, 1952 5 Claims. (Cl. 260569) The present invention relates to stabilized phenylhydrazine.

The best and simplest characteristic for the determination of the degree of purity of phenyl-hydrazine is its solidification point, since already minute impurities result in a considerable drop of the solidification point of the phenyl-hydrazine. Pure phenyl-hydrazine which, for instance, is used in considerable quantities for carrying out syntheses on an industrial scale in the pharmaceutical industry, retains its theoretical solidification point of 19.6 C. only for a short period of time. It soon starts falling to reach only 11 C. after a 6 months storage.

Now we have found that phenyl-hydrazine can be stabilized for a longer period of time by the addition of hexamethylene tetramine, preferably in proportions up to 3 per cent. strength. The addition of the said stabilizmg agent may take place after the manufacture has been terminated or during the distillation for purity of the phenyl-hydrazine by adding dropwise a solution of hexamethylene tetramine saturated in the warmth.

Phenyl-hydrazine stabilized in this manner by the addition of hexamethylene tetramine of 2 per cent. strength has a solidification point of 19.3 C. and retains, even in the presence of metals which catalytically accelerate the decomposition, a solidification point of 19.3 C. to 18.1" C. (=100 per cent. to 98.5 per cent. of phenylhydrazme) for a period of more than 6 months at summer-like temperatures (25 C. to 35 C.) and a lighter shade, whereas non-stabilized phenyl-hydrazine turns slowly darker when being stored.

This stabilized product allows of a storage for a longer period of time which was hitherto impossible, and a shipping in metallic containers without substantial reductlon of the percentage of phenyl-hydrazine. Furthermore, it is always advisable to dispatch stable phenylhydrazme if it is used as preliminary product for important syntheses of remedies.

The following example serves to illustrate the invention.

Example In 500 grams of freshly distilled phenyl-hydrazine solidifying at 19.5 C. containing 99.5 per cent. of pure phenyl-hydrazme, there are dissolved 2 per cent. of hexamethylene tetramine; into the clear solution obtained a a sheet of zinc is laid and the whole is allowed to stand at 25 C. to 35 C. in a closed, brown, glass-stoppered bottle. From time to time samples are taken from the bottle for the determination of the solidification point and the degree of purity of the phenyl-hydrazine, the results obtained being compared with samples of non-stabilized phenyl-hydrazine subjected to the same conditions.

The following table indicates the solidification points and degrees of purity of the two samples depending on the time of storage.

Phenyl-hydrazlne Phenyl-hgdrazlne stabilized non-sta llized Time (months) solidificatlon Point solidification Point Content Percent Content Percent After a 7 months storage under closure the non-stabilized material sustained a loss of about 10 per cent. of its elficacy, whereas the stabilized material sustained a loss of about 1 per cent. under the same conditions. The rapidity of decomposition of the stabilized material after a 7 months storage has thus been reduced to about one tenth of that of the non-stabilized p t. At an increased access of air as well as at elevated temperatures an even greater difference is to be expected.

After a 12 months storage under exclusion of air, stabilized phenyl-hydrazine still has a degree of purity of 96.1 per cent. solidifying at 17.3 C., whereas the non-stabilized product contains only 65.7 per cent. of phenyl-hydrazine.

We claim:

1. A stable phenyl-hydrazine, wherein hexamethylene tetramine is present in a proportion of l to 3 per cent. 2. A stable phenyl-hydrazine, wherein hexamethylene tetramine is present in a proportion of about 2 per cent.

3. A process for the manufacture of a stable phenylhydrazine, comprising addition of hexamethylene tetramine in a proportion of l to 3 per cent. to phenyl-hydrazine.

4. A process for the manufacture of a stable phenylhydrazine, comprising addition of hexamethylene tetramine in a proportion of l to 3 per cent. during the distillation for purity of phenyl-hydrazine.

5. A process for the manufacture of a stable phenylhydrazine, comprising addition of hexamethylene tetramine in a proportion of 1 to 3 per cent. after the manufacture of phenyl-hydrazine.

No references cited. 

1. A STABLE PHENYL-HYDRAZINE, WHEREIN HEXAMETHYLENE TETRAMINE IS PRESENT IN A PROPORTION OF 1 TO 3 PER CENT.
 3. A PROCESS FOR THE MANUFACTURE OF A STABLE PHENYLHYDRAZINE, COMPRISING ADDITION OF HEXAMETHYLENE TETRAMINE IN A PROPORTION OF 1 TO 3 PER CENT. TO PHENYL-HYDRAZINE. 